The primary functions of the Clinical Core are in planning and implementing 3D conformal radiation therapy for patients chosen for the clinical studies of this Program Project. The Clinical Core is involved in the development of treatment protocols, is primarily responsible for obtaining patient specific information and for designing treatment plans, and it plays a key role in assuring the safe and accurate implementation of the multi-field treatments. In carrying out these tasks, the Clinical Core draws on and coordinates the resources of the other Cores. Specifically, the Clinical Core uses the programs developed by the Computer Core and the dosimetric data collected by the Dosimetry Core. In addition, with the progress of the Program Project, when new treatment planning tools become available from Research Project II, as well as new dosimetric and calculational techniques from Research Project III, the Clinical Core will test these programs and implement them. The Clinical Core will also provide support to the Research Projects. It provides support for conducting Research Project I (Clinical Investigations). For research on plan evaluation (Project II) and patient set-up uncertainty (Project III), the Clinical Core will coordinate the collection of clinical data, and participate in their evaluation. It will also support the computer-aid optimization project (Research Project II) by providing feedback and clinical evaluation. In as much as that we shall use equipment such as the multi-leaf collimators and the on-line imagers, which are new technologies, we plan to evaluate them and develop quality assurance protocols, and procedures for their use. The Clinical Core will also participate in the development of the methods and procedures to verify the accuracy of the dose delivery using on-line imager and in-vivo dosimetry.